1. Field of the Invention
This invention relates to an air circuit breaker, and, more particularly, it is concerned with an air circuit breaker having an improved supporting mechanism for an energy accumulating spring to close a pair of contact points.
2. Description of the Prior Art
In general, this type of circuit breaker is not only required to have good operability in the on-and-off instructions to an operating handle to accumulate pressure force in an energy accumulating spring, but also highly expected to be simplified in its construction and be reduced in its overall dimension.
As this type of the circuit breaker, there has so far been known one as disclosed in, for example, Japanese Utility Model Publication No. 52604/1978. The circuit breaker as taught in this invention uses, as its basic construction, a tension coil spring as the energy accumulating spring to build up energy therein by a push-down operation of the operating handle which is pivotally supported in a housing of the circuit breaker in a rotatable manner and projects outward of the front face of the breaker housing, with which latching device for opening and closing the contact points and latch-releasing device are combined.
In the above-described construction, however, since the energy accumulating spring is the tension coil spring, if it is intended to impart sufficient energy accumulating force to the energy accumulating spring by the push-down operation of the handle, there would arise various problems such that the spring should be disposed, with much trouble and inconvenience, at a place where the spring in its state of having accumulated therein the maximum energy does not occupy a space for arrangement of other component elements; in addition, a construction between the base end of the operating handle and the energy accumulating spring becomes complicated due to presence of an energy accumulating link, an energy accumulating plate, and others; and, besides such complicacy in the construction, since the arranging relationship among the component parts is subjected to restriction, the operating members for closing the contacts, and so on become further difficult to be installed at the side of the front face of the housing where the operation can be done easily.
With the abovementioned points of problem in mind, the present invention successfully solved these problems by use of a compression coil spring as the energy accumulating spring. On the other hand, however, there occurred such a shortcoming that a spring holder for preventing the so-called "collapse" in the energy accumulating energy at the time of its compression became inevitably expensive.
This will be explained hereinbelow in reference to FIG. 1. In the drawing, a reference numeral 332 designates a bearing member fixed on a breaker housing 1 with a bolt 336 and a nut 337. On this bearing member 332, there is rotatably supported a hinge pin 326, on which a disk-shaped first spring holder 335 has been fixed by welding. A reference numeral 338 designates a second spring holder, which is connected with a closed arm 26 through a pin 315 at its distal end part. A numeral 31 refers to an energy accumulating spring made of a compression coil spring, one end part 31b of which is supported on the first spring holder 335, and the other end part 31a of which is stopped and held at a collar portion 333 in a manner to embrace the outer periphery of the shaft 339 of the second spring holder 338.
The abovementioned second spring holder 338 is subjected simultaneously to an urging force to the side of the first spring holder 335 and a rotational force in the clockwise direction by the counter-clockwise rotation of the closed arm 26 with a certain definite radius of gyration R. At this instant, there is effected compression of the energy accumulating spring 31 between the collar 333 of the second spring holder 338 and the first spring holder 335. At the same time, both first and second spring holders 335 and 338 and the energy accumulating spring 31 are rotated together at the hinge pin 326 so as to correspond to movement of the link 26, while collapsing of the energy accumulating spring is prevented by the shaft 339 of the second spring holder 338.
In the above-described construction, with a view to supporting the end part 31a of the energy accumulating spring 31 with good stability, the collar 333 of the second spring holder 338 is formed in a disc-shape so that it may support the entire circumference of the abovementioned end part 31a of the spring 31. In contrast to this, the second spring holder 338 is formed by chipping a single monolithic rod. On account of this, the formation of the second spring holder 338 having the collar 333 as mentioned above necessitates use of a raw material (round rod) having a large diameter, which disadvantageously invited increase in the production cost thereof.
Further, since the welding technique is employed for fixing the dish-shaped first spring holder 335 to the hinge pin 326, the assembling efficiency is rather inferior. In addition, the number of component parts for the holder base structure including the first spring holder 335 become increased to also invite disadvantageously rise in the production cost.